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// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package pools
import (
"fmt"
"sync"
"time"
)
// Numbered allows you to manage resources by tracking them with numbers.
// There are no interface restrictions on what you can track.
type Numbered struct {
mu sync.Mutex
empty *sync.Cond // Broadcast when pool becomes empty
resources map[int64]*numberedWrapper
}
type numberedWrapper struct {
val interface{}
inUse bool
purpose string
timeCreated time.Time
timeUsed time.Time
}
func NewNumbered() *Numbered {
n := &Numbered{resources: make(map[int64]*numberedWrapper)}
n.empty = sync.NewCond(&n.mu)
return n
}
// Register starts tracking a resource by the supplied id.
// It does not lock the object.
// It returns an error if the id already exists.
func (nu *Numbered) Register(id int64, val interface{}) error {
nu.mu.Lock()
defer nu.mu.Unlock()
if _, ok := nu.resources[id]; ok {
return fmt.Errorf("already present")
}
now := time.Now()
nu.resources[id] = &numberedWrapper{
val: val,
timeCreated: now,
timeUsed: now,
}
return nil
}
// Unregiester forgets the specified resource.
// If the resource is not present, it's ignored.
func (nu *Numbered) Unregister(id int64) {
nu.mu.Lock()
defer nu.mu.Unlock()
delete(nu.resources, id)
if len(nu.resources) == 0 {
nu.empty.Broadcast()
}
}
// Get locks the resource for use. It accepts a purpose as a string.
// If it cannot be found, it returns a "not found" error. If in use,
// it returns a "in use: purpose" error.
func (nu *Numbered) Get(id int64, purpose string) (val interface{}, err error) {
nu.mu.Lock()
defer nu.mu.Unlock()
nw, ok := nu.resources[id]
if !ok {
return nil, fmt.Errorf("not found")
}
if nw.inUse {
return nil, fmt.Errorf("in use: %s", nw.purpose)
}
nw.inUse = true
nw.purpose = purpose
return nw.val, nil
}
// Put unlocks a resource for someone else to use.
func (nu *Numbered) Put(id int64) {
nu.mu.Lock()
defer nu.mu.Unlock()
if nw, ok := nu.resources[id]; ok {
nw.inUse = false
nw.purpose = ""
nw.timeUsed = time.Now()
}
}
// GetOutdated returns a list of resources that are older than age, and locks them.
// It does not return any resources that are already locked.
func (nu *Numbered) GetOutdated(age time.Duration, purpose string) (vals []interface{}) {
nu.mu.Lock()
defer nu.mu.Unlock()
now := time.Now()
for _, nw := range nu.resources {
if nw.inUse {
continue
}
if nw.timeCreated.Add(age).Sub(now) <= 0 {
nw.inUse = true
nw.purpose = purpose
vals = append(vals, nw.val)
}
}
return vals
}
// GetIdle returns a list of resurces that have been idle for longer
// than timeout, and locks them. It does not return any resources that
// are already locked.
func (nu *Numbered) GetIdle(timeout time.Duration, purpose string) (vals []interface{}) {
nu.mu.Lock()
defer nu.mu.Unlock()
now := time.Now()
for _, nw := range nu.resources {
if nw.inUse {
continue
}
if nw.timeUsed.Add(timeout).Sub(now) <= 0 {
nw.inUse = true
nw.purpose = purpose
vals = append(vals, nw.val)
}
}
return vals
}
// WaitForEmpty returns as soon as the pool becomes empty
func (nu *Numbered) WaitForEmpty() {
nu.mu.Lock()
defer nu.mu.Unlock()
for len(nu.resources) != 0 {
nu.empty.Wait()
}
}
func (nu *Numbered) StatsJSON() string {
return fmt.Sprintf("{\"Size\": %v}", nu.Size())
}
func (nu *Numbered) Size() (size int64) {
nu.mu.Lock()
defer nu.mu.Unlock()
return int64(len(nu.resources))
}
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